According to a continuous demand for improvement in vehicle fuel efficiency and regulations regarding discharge of exhaust in each country, a demand for an environmentally-friendly vehicle has been increased, and a hybrid vehicle and a fuel cell vehicle have become alternatives for the demand. Although the hybrid vehicle may be different from the fuel cell vehicle and an electric vehicle, here, the hybrid vehicle is defined as a vehicle provided with one or more batteries for using energy stored therein as driving power of the vehicle, including a general electric vehicle and the fuel cell vehicle.
The hybrid vehicle has an engine and a motor as power sources. Optimal output torque of the hybrid vehicle depends on how to combine and operate the engine and the motor according to a running state. The hybrid vehicle may be a transmission mounted electric device (TMED) type of hybrid vehicle or a flywheel mounted electric device (FMED) type of hybrid vehicle.
When the hybrid vehicle runs, a traction control system (TCS) sends a request for torque reduction control to a vehicle controller connected by a network to reduce torques of the engine and the motor when a wheel slip occurs at a driving wheel. In response to the request from the TCS, the vehicle controller compares a current output torque with a torque requested from the TCS to determine execution conditions of torque reduction control and sets a torque reduction value. The vehicle controller then reduces the output torques of the engine and the motor to prevent wheel slip from occurring for stable operation.
When the wheel slip does not occur according to the torque reduction control by the vehicle controller, the TCS sends a request for release of the torque reduction control to the vehicle controller. In response to the release request from the TCS, the vehicle controller restores the output torques of the engine and the motor to demand torque for driving.
When a torque reduction control of a TCS is released in a vehicle including one power source, since output torque of the one power source may be smoothly changed, an abrupt change of the output torque may be prevented. However, when two power sources are restored in driving demand torque in the hybrid vehicle in which two or more power sources, for example, the engine and the motor, are operated, since a step-like difference in torque commands and response performance may occur between the two power sources, launching linearity may deteriorate and an abrupt impact may occur.
In addition, when the torque reduction control of the TCS is released in the vehicle including the two or more power sources and output torque of a last operated power source is abruptly changed, even though a total sum of driving demand torque is the same, actual output torques may be different according to each dynamic characteristic of the power sources, thus drivability may deteriorate.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.